1. Field of the Invention
This invention relates to the winding of a traveling paper web, such as is produced by a papermaking machine. More particularly, this invention relates to the construction of either a support drum or a rider roll, or both, for use in a winder for winding such a traveling paper web. Still more particularly, this invention relates to the construction of a support drum or rider roll having an elastomeric cover having a unique combination of Poisson's ratio, absolute hardness and effective hardness to provide a relatively soft nip in support of the wound paper roll while utilizing a relatively hard elastomeric cover.
2. Description of the Prior Art
In the papermaking industry, a common form of winder for winding the substantially endless paper web produced by the papermaking machine comprises a pair of spaced, parallel support drums for supporting the wound paper roll being wound from the traveling paper web.
It is known in the papermaking industry to have winder support drums with grooves to permit the paper roll being wound to be turned with the purpose of encouraging less slippage between it and the support drum. Also, such grooves may provide a means to reduce any boundary layer air film between the drum and the paper roll. Such grooves can take several forms, such as, for example, spiral grooves, Chevron, or herringbone patterned.
It has also been contemplated to cover the support drums with an elastomeric material, such as rubber, in an attempt to provide a larger support area for the increasingly heavy wound paper roll on the cylindrical surface of the support drum. Some of such rubber covered drums have also been grooved. Examples of prior art types of grooving and support drum covers are shown in U.S. Pat. Nos. 1,867,550; 3,098,619; 4,541,585 and British Patent No. 417,769. While the prior art includes roll and support drums having elastomeric covers, the practice heretofore in the papermaking industry was to construct these covers with a hardness of 85 Shore "A", or greater; only rarely have covers had a hardness as soft as 75 Shore "A". On the Shore "A" scale, readings approaching 100 are relatively hard, and readings approaching 25 are relatively soft.
Grooved winder drums, grooved elastomeric covered winder drums and elastomeric covered winder drums all have some operational advantages and efficiencies which are generally associated with their ability to better support the paper roll being wound with less slippage, less internal stress, and more control of the winding process and desired parameters. This is particularly true during periods when the rotational speed of the wound paper roll is changing. However, such prior configurations also had inherent deficiencies.
If the non-grooved elastomeric material was too hard, it essentially operated like a solid metallic support drum, which negated any advantage, such as a larger support area, that an elastomeric cover provides. Softer elastomeric covers, which might provide such a larger wound web roll support area, were not believed to be economically or operationally viable.
Therefore, while fundamental configurations, such as providing support drums with elastomeric covers and grooving such drums, have long been known, there has been a long-felt need for a paper winder support drum having a grooved elastomeric cover which provides a relatively softer, wider nip and relatively long service during operation.